add the 'extension' command framework

This patch introduces a facility which would allow to compile in
callbacks for arbitrary commands passed over various communication
protocols.

Typically this will be used for testing, when various test commands
are multiplexed over an existing protocol.

The callbacks are associated with 16 bit command codes. On input the
callback receives a buffer, containing the command's argument, the
size of the command argument and the maximum size of the buffer. On
output the callback stores processing result in the same buffer and
updates the size to the actual amount of returned data.

Callback descriptors are stored in a dedicated read only section which
is scanned by extension_route_command() to find a callback associated
with a certain command code.

A console channel is also being introduced to allow controlling
console output generated by extension commands handlers.

BRANCH=none
BUG=chrome-os-partner:47524
TEST=none yet

Change-Id: I8ae16a78ca7d72176a5e7f74dd7a232078e7c06c
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/312586
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 36 insertions, 0 deletions

diff --git a/common/extension.c b/common/extension.c
new file mode 100644
index 0000000000..a588ce892e
--- /dev/null
+++ b/common/extension.c
@@ -0,0 +1,36 @@
+/* Copyright 2015 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "byteorder.h"
+#include "console.h"
+#include "extension.h"
+#include "link_defs.h"
+
+#define CPRINTF(format, args...) cprintf(CC_EXTENSION, format, ## args)
+
+void extension_route_command(uint16_t command_code,
+			    void *buffer,
+			    size_t in_size,
+			    size_t *out_size)
+{
+	struct extension_command *cmd_p;
+	struct extension_command *end_p;
+
+	cmd_p = (struct extension_command *)&__extension_cmds;
+	end_p = (struct extension_command *)&__extension_cmds_end;
+
+	while (cmd_p != end_p) {
+		if (cmd_p->command_code == command_code) {
+			cmd_p->handler(buffer, in_size, out_size);
+			return;
+		}
+		cmd_p++;
+	}
+
+	CPRINTF("%s: handler %d not found\n", __func__, command_code);
+
+	/* This covers the case of the handler not found. */
+	*out_size = 0;
+}